Use \[ .. \] for display math instead of $$ ... $$

$$ .. $$ is not recommended for use with LaTeX, see http://tex.stackexchange.com/questions/503

Author: TorbjornT

docs/source/changelog.rst

@@ -28,6 +28,7 @@ Changed
 - `.Tabular.add_row` now accepts a list of mappers
 - `.Tabular.add_row` now accepts cells as arguments, so they don't have to be
   wrapped in a `list` or `tuple` anymore.
+- Changed from using ``$$ ... $$`` for displaymath to using ``\[ ... \]``.
 
 Added
 ~~~~~

pylatex/math.py

@@ -13,6 +13,8 @@
 class Math(Container):
     """A class representing a math environment."""
 
+    packages = [Package('amsmath')]
+
     content_separator = ' '
 
     def __init__(self, *, inline=False, data=None):
@@ -39,7 +41,7 @@ def dumps(self):
 
         if self.inline:
             return '$' + self.dumps_content() + '$'
-        return '$$%\n' + self.dumps_content() + '%\n$$'
+        return '\\[%\n' + self.dumps_content() + '%\n\\]'
 
 
 class VectorName(Command):